Various types of optoelectronic displays are known in the art. These include, for example, Liquid Crystal Displays (LCDs), ElectroLuminescent (EL) displays, and Plasma Displays (PDs).
Multicoloured displays typically comprise a plurality of pixels, each pixel comprising a plurality of sub-pixels. In a full colour display, red, green, and blue sub-pixels are provided. The sub-pixels are defined by a colour-forming layer. The colour-forming layer may be a light-emissive layer comprising a plurality of discrete light-emissive regions of different light-emissive material defining the sub-pixels. For example, an EL display has such a light-emissive layer disposed between electrodes which are patterned so as to be able to address the individual sub-pixels which correspond to the discrete light-emissive regions of the light-emissive layer.
Alternatively, the colour-forming layer may be a colour filter comprising a plurality of discrete regions of different colour defining the sub-pixels. For example, an LCD may have such a filter with a white backlight and a liquid crystal arrangement for addressing the individual sub-pixels that correspond to the discrete coloured regions of the filter.
Various different arrangements for the pixels and the sub-pixels of a light-emissive display have been proposed in the prior art. FIG. 1 shows a standard pixel arrangement in which each pixel 2 comprises a single red sub-pixel 4, a single green sub-pixel 6 and a single blue sub-pixel 8, all of which are the same size.
Improvements over the basic arrangement shown in FIG. 1 have been suggested, such as the arrangements disclosed in US 2003/0117423, WO 03/060870 and 2004/0080479. These “checkerboard” arrangements are adapted to provide better visual performance when compared to the standard arrangement shown in FIG. 1. An example is shown in FIG. 2 of the present application, each pixel 2 comprising a central blue sub-pixel 8, with red sub-pixels 4 in one pair of diagonally opposing corners, and green sub-pixels 6 in the other pair of diagonally opposing corners. The sub-pixels are arranged so that around a junction between four adjacent pixels, the sub-pixels alternate between red and green.
A problem with the aforementioned arrangements is that it is difficult to provide an intricately patterned colour-forming layer. Furthermore, depending on the materials and the patterning techniques used, there will be a lower limit to the size of discrete colour-forming regions that can be reliably formed.
Embodiments of the present invention seek to solve the aforementioned problems in the prior art by providing a pixel/sub-pixel arrangement that is easier to manufacture and has good visual performance.